auxdisplay: lcd2s: add error handling for i2c transfers

The lcd2s_print() and lcd2s_gotoxy() functions currently ignore the
return value of lcd2s_i2c_master_send(), which can fail. This can lead
to silent data loss or incorrect cursor positioning.

Add proper error checking: if the number of bytes sent does not match
the expected length, return -EIO; otherwise propagate any error code
from the I2C transfer.

Signed-off-by: Wang Jun <1742789905@qq.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Author: blacksanxx

drivers/auxdisplay/lcd2s.c

@@ -99,18 +99,27 @@ static int lcd2s_print(struct charlcd *lcd, int c)
 {
 	struct lcd2s_data *lcd2s = lcd->drvdata;
 	u8 buf[2] = { LCD2S_CMD_WRITE, c };
+	int ret;
 
-	lcd2s_i2c_master_send(lcd2s->i2c, buf, sizeof(buf));
+	ret = lcd2s_i2c_master_send(lcd2s->i2c, buf, sizeof(buf));
+	if (ret < 0)
+		return ret;
+	if (ret != sizeof(buf))
+		return -EIO;
 	return 0;
 }
 
 static int lcd2s_gotoxy(struct charlcd *lcd, unsigned int x, unsigned int y)
 {
 	struct lcd2s_data *lcd2s = lcd->drvdata;
 	u8 buf[3] = { LCD2S_CMD_CUR_POS, y + 1, x + 1 };
+	int ret;
 
-	lcd2s_i2c_master_send(lcd2s->i2c, buf, sizeof(buf));
-
+	ret = lcd2s_i2c_master_send(lcd2s->i2c, buf, sizeof(buf));
+	if (ret < 0)
+		return ret;
+	if (ret != sizeof(buf))
+		return -EIO;
 	return 0;
 }